The invention relates to a method of preparing functionally valuable products, such as β-glucan, protein, starch and lipid concentrates, from oat. The invention also relates to products thus obtained and to the use thereof. The invention further relates to the use of non-heat-treated or slightly heat-treated oat, fat-extracted with supercritical extraction, in preparing β-glucan, protein and starch concentrates.
Oat is known to contain functionally valuable components, one of which is its important fibre component, β-glucan. β-Glucan has been found to possess, inter alia, a cholesterol-reducing effect that is also positive as regards weight control. In addition, oat also contains other functionally valuable components, such as proteins, starch and lipids, which find use in the food industry, the pharmaceutical industry and cosmetics.
Publications B. E. Knuckles et al., “β-Glucan-Enriched Fractions from Laboratory-Scale Dry Milling and Sieving of Barley and Oats”, Cereal Chemistry, 69(2), 1992, p. 198 to 202 and Y. V. Wu & D. C. Doehlert, “Enrichment of β-glucan in Oat Bran by Fine Grinding and Air Classification”, Lebensmittel.-Wiss. u. Technol., 35, 2002, p. 30 to 33 disclose the preparation of β-glucan-containing fractions from oat and barley by using dry processes, such as milling, sieving and classification. The starting material used is oat, which is at least partly defatted by solvent treatment (n-hexane). This treatment yielded oat fractions having a β-glucan content of at most about 28%. The disadvantage of solvent treatment is that it usually has a denaturing effect on oat proteins and other functionally valuable components. Solvent residues and safety also present problems.
Publication U.S. Pat. No. 6,797,307 B2 (Mälkki et al., Avena Oy) discloses a method for preparing a β-glucan-containing oat fraction by milling and classifying from non-defatted oat (fat content 6 to 7%). The oat used as starting material is heat-treated or heat-stabilized. The publication claims that the method is usable for preparing β-glucan concentrates having a β-glucan content of up to 25%. Heat treatment may have a denaturing effect on the functionally valuable components of oat. The presence of fat, in turn, may have a harmful effect on the shelf life of the products.
Publications U.S. Pat. No. 6,323,338 B1 (Potter et al., Nurture Inc.), WO 2005/120251 A1 (Löv et al., Oy Glubikan Ab), WO 2004/096242 (Redmond & Fielder, Ceapro Inc.), US 2004/0101935 A1 (Vasanthan & Temelli) and WO 2005/122785 A1 (Kvist & Lawther, Biovelop International B.V.) disclose solvent-based methods for preparing β-glucan concentrates from plant material, such a cereal grain, including oat and barley. The β-glucan content of these β-glucan concentrates is higher than that obtained by dry methods, about 87% (U.S. Pat. No. 6,323,338) or 92% (WO 2004/096242), for example. Aqueous solutions or organic solvents, such as ethanol, or combinations of water and organic solvents, for example, are used as solvents. In these methods, β-glucan is usually dissolved in an aqueous solution and recovered therefrom by precipitation, filtering and drying, by membrane techniques or other suitable manners. The preparation of concentrates generally requires plenty of water and/or solvents and much energy required by the drying. In addition, the use of solvents may have a harmful effect on the properties of the product.
An oat fibre preparation (manufacturer Swedish Oat Fiber Kb, distributor Creanutrition) containing 22% β-glucan is also commercially available. It is prepared from heat-treated oat bran or oatmeal by extracting fat with ethanol, whereby the fat content of the finished, enriched fibre is about 4%.